This invention is best suited for the detecting of short circuits occurring across the Vacuum Switch.
In industrial situations, vacuum switches are used to bring high voltage electrical power from main supply lines to their industrial use. The switches can be placed in their open position in order to work on equipment and prevent electrical power to reach the industrial use being worked on. However, if a short circuit should occur across the vacuum switch when the industrial use is being worked on, dangerous and lethal voltage may surge across the switch towards the industrial use. Without an adequate warning system, a repariman may suffer serious injuries.
This invention provides an audio-visual detection of short circuits across vacuum switches or similar devices, and prevents maintenance personnel from inadvertently or unknowingly disengaging the alarm by placing the alarm control panel in a remote place.
Certain prior patents have approached the solution of this problem by monitoring the vacuum switch itself to detect malfunction. U.S. Pat. Nos. 3,594,754 of Roy E. Voshell and 3,403,297 of Donald W. Couch describe methods whereby the pressure in the vacuum type circuit interrupter is measured. U.S. Pat. No. 1,733,904 by Prince is basically a redesign of the vacuum switch itself by incorporating a vacuum gauge or device which would impair the operation of the switch should the vacuum be reduced. U.S. Pat. No. 3,735,201 by May is an arcing time relay which is designed to be used with vacuum circuit breakers, and the primary purpose is detection of the loss of vacuum as manifested by an increase of arcing time. The detection device of this invention is a highly sensitive relay. These patents detect malfunction in the vacuum switch, but do not detect mechanical malfunction such as fused points or other malfunctions which can occur between the vacuum switch and the industrial use. In addition, the detection devices of the vacuum switches are complex and do not utilize the simple principle of using the malfunction voltage itself to excite alarm circuits.
U.S. Pat. No. 3,558,984 by Smith and Gray describes an A. C. System Fault Indicator which utilizes coils as sensing devices and is devised to detect various faults in phase or current in a conductor such as a distribution line. U.S. Pat. No. 3,851,322 by Compoly and Temple detects short circuits in static converters by monitoring line voltages in currents. Both these patents differ from the present invention in at least one aspect in that the present invention monitors an inert circuit.
The above inventions monitor possible malfunctions but in doing so have to use complex monitoring devices. Those detection devices which monitor the vacuum switch only, do not prevent a mechanical malfunction which can occur between the vacuum switch and the industrial use. The present invention uses the voltage of the malfunction itself to excite the warning system.